[MSHARED-1438] Provide protected methods for XRef location construction

This closes #56

src/main/java/org/apache/maven/reporting/AbstractMavenReport.java

@@ -23,6 +23,7 @@
 import java.io.IOException;
 import java.io.OutputStreamWriter;
 import java.io.Writer;
+import java.util.Collections;
 import java.util.Date;
 import java.util.HashMap;
 import java.util.List;
@@ -41,6 +42,8 @@
 import org.apache.maven.doxia.siterenderer.sink.SiteRendererSink;
 import org.apache.maven.doxia.tools.SiteTool;
 import org.apache.maven.doxia.tools.SiteToolException;
+import org.apache.maven.model.ReportPlugin;
+import org.apache.maven.model.Reporting;
 import org.apache.maven.plugin.AbstractMojo;
 import org.apache.maven.plugin.MojoExecution;
 import org.apache.maven.plugin.MojoExecutionException;
@@ -50,6 +53,7 @@
 import org.apache.maven.shared.utils.WriterFactory;
 import org.codehaus.plexus.PlexusContainer;
 import org.codehaus.plexus.component.repository.exception.ComponentLookupException;
+import org.codehaus.plexus.util.PathTool;
 import org.codehaus.plexus.util.ReaderFactory;
 import org.eclipse.aether.RepositorySystemSession;
 import org.eclipse.aether.repository.RemoteRepository;
@@ -461,4 +465,56 @@ public boolean canGenerateReport() throws MavenReportException {
      * @throws MavenReportException if any
      */
     protected abstract void executeReport(Locale locale) throws MavenReportException;
+
+    /**
+     * Returns the (Test) Source XRef location as passthrough if provided, otherwise returns the
+     * default value.
+     *
+     * @param location the XRef location provided via plugin parameter, if any
+     * @param test whether it is test source
+     * @return the actual (Test) Source XRef location
+     */
+    protected File getXrefLocation(File location, boolean test) {
+        return location != null ? location : new File(getReportOutputDirectory(), test ? "xref-test" : "xref");
+    }
+
+    /**
+     * Contructs the (Test) Source XRef location relative to the {@link #getReportOutputDirectory()}
+     * with {@link #getXrefLocation(File, boolean)}.
+     *
+     * @param location the XRef location provided via plugin parameter, if any
+     * @param test whether it is test source
+     * @return the constructed (Test) Source XRef location
+     */
+    protected String constructXrefLocation(File location, boolean test) {
+        String constructedLocation = null;
+        File xrefLocation = getXrefLocation(location, test);
+
+        String relativePath =
+                PathTool.getRelativePath(getReportOutputDirectory().getAbsolutePath(), xrefLocation.getAbsolutePath());
+        if (relativePath == null || relativePath.isEmpty()) {
+            relativePath = ".";
+        }
+        relativePath = relativePath + "/" + xrefLocation.getName();
+        if (xrefLocation.exists()) {
+            // XRef was already generated by manual execution of a lifecycle binding
+            constructedLocation = relativePath;
+        } else {
+            // Not yet generated - check if the report is on its way
+            Reporting reporting = project.getModel().getReporting();
+            List<ReportPlugin> reportPlugins =
+                    reporting != null ? reporting.getPlugins() : Collections.<ReportPlugin>emptyList();
+            for (ReportPlugin plugin : reportPlugins) {
+                String artifactId = plugin.getArtifactId();
+                if ("maven-jxr-plugin".equals(artifactId)) {
+                    constructedLocation = relativePath;
+                }
+            }
+        }
+
+        if (constructedLocation == null) {
+            getLog().warn("Unable to locate" + (test ? " Test" : "") + " Source XRef to link to -- DISABLED");
+        }
+        return constructedLocation;
+    }
 }